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Touch Screen User Interfaces for Older Adults: Button Size and Spacing

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  • TSB Tecnologias
  • Tom Sawyer Software
Conference Paper

Touch Screen User Interfaces for Older Adults: Button Size and Spacing

Abstract and Figures

This study investigated the optimal button size and spacing for touch screen user interfaces intended for use by older adults. Current recommendations in the literature are aimed at general audiences and fail to consider the specific needs of older adults. Three independent variables, button size, button spacing, and manual dexterity were studied in two experiments that measured reaction time, accuracy and user preferences. Design recommendations for touch screen button size and spacing for older adults are stated based on these experiments. The paper also discusses the role of manual dexterity in designing appropriate touch screen interfaces for older adults.
Content may be subject to copyright.
C. Stephanidis (Ed.): Universal Access in HCI, Part I, HCII 2007, LNCS 4554, pp. 933–941, 2007.
© Springer-Verlag Berlin Heidelberg 2007
Touch Screen User Interfaces for Older Adults: Button
Size and Spacing
Zhao Xia Jin1, Tom Plocher2, and Liana Kiff2
1 Honeywell Technology Solutions Laboratory,
Shanghai, China
Zhao.Xia.Jin@Honeywell.com
2 Honeywell Automation and Control Solutions Laboratory,
Minneapolis, Minnesota, USA
{tom.plocher,liana.kiff}@honeywell.com
Abstract. This study investigated the optimal button size and spacing for touch
screen user interfaces intended for use by older adults. Current recommendations
in the literature are aimed at general audiences and fail to consider the specific
needs of older adults. Three independent variables, button size, button spacing,
and manual dexterity were studied in two experiments that measured reaction
time, accuracy and user preferences. Design recommendations for touch screen
button size and spacing for older adults are stated based on these experiments.
The paper also discusses the role of manual dexterity in designing appropriate
touch screen interfaces for older adults.
Keywords: older adults, usability, touch screen, user interface design.
1 Introduction
Touch screens are widely used in applications such as information kiosk displays,
ATMs and home systems for environmental control, security and health care. The
intuitiveness and ease of operation of touch screens has made them popular in
products for older adults. However, to achieve these benefits, it is critical for the
designer to trade off the target size and target spacing associated with the control
buttons in the touch sensitive area of the display. This is especially important when
the screen space is very limited. While recommendations and previous studies exist in
the literature, these are aimed at general users rather than older adults.
For systems using touch screens, the ISO [1] recommends that the size of the
touch-sensitive area should be at least equal to the breadth of the index finger distal
joint for the ninety-fifth percentile male. The EIA [2] recommends that the minimal
touch-sensitive size should be 19.05 mm [2]. Pfauth and Priest identified key size as
an important factor in touch screen use when the interface involved a hierarchical
menu display [3]. Other studies revealed that larger key sizes led to better
performance in touch screen interfaces that support numeric keypad entry or menu
entry [4, 5, 6, 7, 8, 9,10].
934 Z.X. Jin, T. Plocher, and L. Kiff
For a matrix of buttons such as an iconic navigation panel or numeric keypad, the
size of the spaces between adjacent buttons must also be considered. For touch-sensitive
screens designed for first-contact touch activation, the ISO [1] recommends providing
an inactive space at least 5 mm wide around each touch target. The EIA [2]
recommends that the spacing between touch sensitive areas should be at least 6 mm.
Previous studies revealed some interesting results with spacing. For example, Scott and
Conzola's [11] results support the use of compressed (2mm or less) inter-key spacing in
keypad designs. Martin [6] recommended compressed 6 mm inter-key spacing for
square keys. Colle and Hiszem [8] recommended that 1 mm spacing should be used if
sufficient space is available and spacing as small as 0 mm might be acceptable if space
is very limited. Sun's study [9] with firefighters also indicated that the size of button
spacing usually did not affect performance. However, when the button size is very
small, such as 20 x 20 pixels (6 mm on Sun's display), zero-inch spacing decreased
performance. Sun's experiment also showed that there is a tradeoff between speed and
accuracy that depends on spacing. Larger spacing resulted in fewer errors, but increased
the reaction time. Beaton and Weiman [4] also found that users preferred vertical
spacing of 5 or 10 mm and horizontal spacing of 10 mm.
The studies described above set some general guidelines for touch screen button
size and spacing, but they do not consider the special characteristics of older adults
that might affect the use of touch screen interfaces. Carmeli, et al. [12] provides an
extensive review of changes in the aging hand that affect manual dexterity. Goggin
and Meeuwsen [13] found age-related differences in the spatial aiming and pointing
movements commonly associated with manual dexterity, with older adults
emphasizing accuracy over speed. Pratt, et al. [14] found that hand pointing
movements of older adults were qualitatively different than younger adults. Ketcham,
et al.[15] had younger and older adults perform a similar aiming task, varying target
size and position on a screen. They found that decreasing target size caused older
adults to make more corrective movements than younger adults as they propelled their
hand toward the target, which resulted in slower reaction times.
The study reported here sought to determine the optimal control button size and
spacing for touchscreen-based user interfaces for older adults. Two experiments were
designed to test researchers' hypotheses. Experiment 1 was a touch test with only a
single button. The test simulated a device that has only one key or two or more non-
adjacent keys. Experiment 2 was a touch test with multiple buttons and simulated a
device in which adjacent keys are laid out in rows.
2 Experiment 1 – Single Button Touch Test
2.1 Design
Subjects. Twenty-six older adults (13 female and 13 male) aged from 53 to 84 years
(mean = 71.81, SD = 6.91) gave their informed consent to participate in Experiment
1. All subjects were right-handed. Subjects were recruited from Social Welfare of
Shanghai-PuTuo Area (13 persons) and the elder college of East China Normal
University (13 persons).
Touch Screen User Interfaces for Older Adults: Button Size and Spacing 935
Experimental Design. The experiment used a 2 x 9 repeated measure design.
Pegboard performance had two levels, high PB and low PB, and was treated as a
between-subjects factor. Button size was treated as a within-subjects factor and had
nine levels: 6.35 mm, 8.89 mm, 11.43 mm, 13.97 mm, 16.51 mm, 19.05 mm, 21.59
mm, 24.13 mm, and 26.67 mm). The only dependent variable was reaction time (RT).
2.2 Procedures
Peg Board Test. All subjects' were tested using the Peg Board Test published by The
Morrisby Organisation [16]. This test measures manual dexterity using a straight-
forward task that requires candidates to assemble pins, washers and collars and place
them in holes.
Single Button Touch Test. After the pre-tests, all subjects were asked to perform the
single button touching test. Before the formal testing, they were given a 12-trial
practice. During the test, a single target button appeared in a random position within a
designated 160 mm x 160 mm area at the center of the screen. The subjects were
asked to touch the target button as quickly and accurately as possible. Within 500 ms
after the subject touched the target, the next target would appear. Subjects were asked
to place their finger in a standard ready position, the lower right corner of the touch
screen. All stimuli in each condition appeared randomly to avoid ordering effects. A
total of eight repeated trials were measured in each condition for each subject.
Equipment. The experiment was set up in a room with daylight lamp lighting. An
ELO 17 inches Touch Screen LCD (Model number ET1725L-8uWF-1, 442072-001)
was used at a resolution of 1024 x 768. The subjects were asked to sit in front of the
touch screen and adjust their position relative to the screen until they were at a
comfortable viewing distance. Also, they were allowed to adjust the tilt of the display
screen for a comfortable viewing angle, typically 75º relative to the desk.
2.3 Results
Peg Board Test. Based on Peg Board Test scores, each subject was assigned to one
of two groups, a High PB (Peg Board Test) group and a Low PB group. Subjects were
scored on two Peg Board subtests, preferred hand and both hands. Higher Peg Board
Test scores indicate greater manual dexterity. Subjects whose PB Score (Right Hand)
was greater than or equal to 12 and PB Score (Both Hands) greater than or equal to 18
were placed in the High PB group.
Single Button Touch Test. By design, accuracy on this test was 100%. A trial began
only after the button in the previous trial had been touched. The buttons were touched
on every trial. Therefore, only data on reaction time was recorded and analyzed.
Figure 1 shows the mean RT for the entire sample of 26 subjects as a function of
button size. Repeated measure analysis revealed that the main effect of button size
was significant, F(8, 192) = 27.770, p*** < .001, indicating that RT decreased as the
button size increased.
936 Z.X. Jin, T. Plocher, and L. Kiff
One way ANOVA revealed that the Mean RT at size = 6.35 mm was significantly
longer than the mean RT at sizes > 6.35 mm. The mean RT at size = 8.89 mm was
significantly longer than the mean RT at sizes >= 13.97 mm. No significant difference
was found between the Mean RTs at 11.43 mm, 13.97 mm, 16.51 mm, 19.05 mm,
21.59 mm, 24.13 mm, and 26.67 mm. Also shown in Figure 1 is a slight increase in
the Mean RT at size = 24.13 mm which suggests that faster RTs could not be obtained
by increasing button size further.
Figure 2 compares the RT performance of the High PB to the Low PB group at
various button sizes. Analysis showed no significant group effect of PB level, F(1, 24) =
2.900, p > .05, and no significant interaction of PB x Size, F(8, 192) = .203, p > .05,
even though the High PB Group (Mean =1074.05, SD = 373.07) was 21.83 % faster
than the Low PB group (Mean = 1373.91, SD = 480.22). This indicates that manual
dexterity as measured by the Pegboard test does not significantly affect the
performance in touching an isolated button on the screen.
3 Experiment 2 – Multiple Button Touch Test
3.1 Design
Subject. Fourty older adults (22 female and 18 male) aged from 50 to 85 years (Mean
= 70.08, SD = 6.39) participated in Experiment 2. All subjects were right-handed.
Subjects were recruited from Social Welfare of Shanghai-PuTuo Area (23 persons)
and the elder college of East China Normal University (17 persons). All 26 subjects
who participated in Experiment 1 also participated in Experiment 2.
Experimental Design. The experiment used a 2 x 6 x 5 repeated measure design. Peg
Board performance had two levels, high PB and low PB and was a between-subjects
factor. Button size was treated as a within-subjects factor and had six levels: 11.43
mm, 13.97 mm, 16.51 mm, 19.05 mm, 21.59 mm, and 24.13 mm. Spacing also was
treated as a within-subjects factor and had five levels: 0 mm, 3.17 mm, 6.35 mm, 12.7
mm and 19.05 mm. Dependent variables were reaction time (RT) and accuracy.
Fig. 1. Mean RT (ms) on a single button
touch test for all subjects at different button
sizes
0.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
4000.00
6.35 8.89 11.43 13.97 16.51 19.05 21.59 24.13 26. 67
Button Size (mm )
Mean RT (ms)
0.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
4000.00
6.35 8.89 1 1.43 13.97 16.51 19.05 21.59 24.13 26.67
Button Size (mm)
Mean RT (ms)
High PB
Low PB
Fig. 2. Mean RT(ms) on a single button touch
test for the High PB group and Low PB group
at different button sizes
Touch Screen User Interfaces for Older Adults: Button Size and Spacing 937
3.2 Procedures and Equipment
As in Experiment 1, all subjects' were tested for manual dexterity using the Peg Board
Test. Following the pre-tests, all subjects were given a 12-trial practice on the
multiple button touch test and then asked to perform the formal test.
The multiple button touch test worked in the following manner. A button with a
picture on it appeared at the top of the screen. A 3 x 3 matrix of buttons with pictures
simultaneously appeared directly below it on the screen. The subjects' task was to
select the button from the 3 x 3 matrix that matched the button at the top of the screen,
e.g. had the same picture as the one at the top. Subjects were told to use their finger to
touch this button in the matrix as quickly and accurately as they could. Within 500 ms
after touching a target in the matrix, the next trial would appear. Subjects were asked
to place their finger in a standard ready position, the lower right corner of the touch
screen. After the touch testing was completed, the subjects were asked to choose the
most comfortable and preferred button size, horizontal spacing, and vertical spacing.
All stimuli in different conditions appeared in random to avoid ordering effects. A
total of 5 repeated trials were measured in each condition for each subject.
3.3 Results
Peg Board Test. As in experiment 1, all subjects were separated into one of two
groups based on their Peg Board Test scores. Subjects whose PB Score (Right Hand)
was greater than or equal to12 and PB Score (Both Hands) greater than or equal to 18
were placed in the High PB group. Those scoring lower than this were placed in the
Low PB group.
Multiple Button Touch Test. The data of 40 subjects were analyzed using a 2 x 6 x 5
repeated measure analysis, with the factors PB Level (2), Button Size (6), and Button
Spacing (5). Reaction Time (RT), Accuracy and Preferences were analyzed. The first
and second responses and the extremes (over 1.5 SD) were excluded from the
statistical analysis. Excluded data comprised only 0.033% of all data collected.
Reaction Time. Size and Spacing Main Effects. Figure 3 shows the Mean RT for each
combination of button size and spacing. Repeated measures analysis of RT revealed
that the main effect of button size was significant, F(5, 190) = 32.443, p***< .001. The
Mean RT decreased as the button size increased. One way ANOVA analysis of size
revealed that the mean of RT at size = 11.43 mm is significantly longer than the mean
of RT at size > 11.43 mm. The mean of RT at size = 13.97 mm is significantly longer
than the mean of RT at size > 13.97 mm. No significant difference in RT was found
between the sizes 16.51 mm, 19.05 mm, 21.59 mm, and 24.13 mm.
The effect of button spacing was also significant, F (4, 152) = 7.682, p***< .001. The
subjects showed the longest mean RT at a spacing of 19.05 mm (Mean = 1881.73, SD
= 846.8) and achieved the shortest mean RT at a spacing of 0 mm (Mean = 1732.01,
SD = 737.78). One way ANOVA analysis of spacing revealed that the mean RT at
spacing = 19.05 mm was significantly longer than the mean RT at spacing < 19.05
mm. The mean of RT at spacing = 12.7 mm was significantly longer than the mean
RT at spacing = 0. No significant difference was found between the mean RT at other
spacings: 0 mm, 3.17 mm, and 6.35 mm.
938 Z.X. Jin, T. Plocher, and L. Kiff
Fig. 3. Mean RT (ms) for all subjects at
different button sizes and spacings in a
multiple-button touch test
Fig. 4. Mean RT (ms) of each group for
button sizes in a multiple-button touch test
1200.00
1400.00
1600.00
1800.00
2000.00
2200.00
2400.00
2600.00
11.43 13.97 16.51 19.05 21.59 24.13
Button Size ( mm )
Mean RT (ms)
High PB
Low PB
Effects of Manual Dexterity on RT. Figure 4 shows the significant main effect of manual
dexterity as measured by the Peg Board Test, F(1, 38) = 25.545, P*** < .001. Reaction
Time of the High PB group (Mean = 1384, SD = 422.5) was 34.69% shorter than that of
the Low PB group (Mean = 2119, SD = 890.4). No significant interaction was found,
but there was a trend for the interaction effect of Size x Peg Board Test Level,
F(5,190) = 2.739, P*(Sphericity Assumed) = .021 < .05, P(Low bound) = .107 > .01.
For the High PB group, a one-way ANOVA revealed that RT at button
size = 11.43 mm is significantly longer than at sizes > 11.43 mm. RT at size = 13.97
mm is significantly longer than at sizes = 19.05 mm or 24.13 mm. There were no
differences between button sizes of 19.05 mm, 21.59 mm, and 24.13 mm. For the
Low PB group, a one-way ANOVA indicated that RT at size = 16.51 mm is
significantly longer than sizes > 11.43 mm. RT at size = 13.97 mm is significantly
longer than sizes > 13.97 mm.
Also, for the High PB group, the RT curve becomes flat at 16.51 mm, while the RT
curve for the Low PB group becomes flat at 19.05 mm. This might explain the trend
for an interaction effect on RT between size and Peg Board level. There was no
significant interaction of size x PB, space x PB or size x space x PB.
Accuracy. Size and Spacing Main Effects. As Figure 5 shows, as a whole, the
subjects performed the multiple button test with high accuracy (average correct
responses = 98.85%, SD = 0.05). Repeated measure analysis of accuracy revealed a
significant main effect of Size, F(5,190) = 5.237, p*** < .001. Accuracy tended to
increase with button size from 11.43 mm to 19.05 mm, where it was highest
(Mean = 99.6 %, SD = 0.002). Accuracy decreased a little for larger button sizes of
21.59 mm, and 24.13 mm. However, even at these button sizes, accuracy was still
99.4% and 99.2%, respectively. There was no significant main effect of spacing on
accuracy, F(4, 152) = 1.612, p > .05.
Effects of Manual Dexterity on Accuracy. The effect of manual dexterity on accuracy
was not significant, F(1,38) = 1.049, P > .05 . However, Figure 6 shows that for all
button sizes smaller than 24.13 mm, the High PB group tended to perform with higher
accuracy than the Low PB group. However, the differences were not statistically
significant. Also, there was no significant interaction on accuracy for size x PB, space
x PB or size x space x PB.
1500.00
1600.00
1700.00
1800.00
1900.00
2000.00
2100.00
2200.00
11.43 13.97 16.51 19.05 21.59 24.13
Button Size (mm)
Mean RT (ms)
0 mm
3.17 mm
6.35 mm
12.7 mm
19.05 mm
Touch Screen User Interfaces for Older Adults: Button Size and Spacing 939
95.0%
96.0%
97.0%
98.0%
99.0%
100.0%
11.43 13.97 16.51 19.05 21.59 24.13
Button Size (mm)
Mean Accurac y (%)
0 mm
3.17 mm
6.35 mm
12.7 mm
19.05 mm
95
95.5
96
96.5
97
97.5
98
98.5
99
99.5
100
100.5
11.43 13.97 16.51 19.05 21.59 24. 13
Button Si ze (mm)
Mean Accuracy (%
)
High PB
Low PB
Fig. 5. Mean accuracy (%) for all subjects at
different button sizes and spacings in multiple
button test
Fig. 6. Mean accuracy (%) of each group a
t
different button sizes in a multiple button
touch test
Subjective Preferences. Overall Button Size. Chi-Square Tests of expressed subject
preferences revealed a significant difference at different button sizes, x2 = 14 df = 4,
P** < 0.01. The subjects favored button sizes of 16.51 mm and 19.05 mm.
Manual Dexterity and Button Size Preferences. Analyzing the preferences of each PB
group separately revealed a statistically nonsignificant, but rather clear trend in
preference for a button size of 19.05 mm in the High PB group, x2 = 8.155 df = 4,
0.05 < p < 0.1. In contrast, the Low PB group's preferences were distributed across a
range of the larger button sizes: 16.51 mm (31.8%), 19.05 mm (22.7%), 21.59 mm
(18.2%) and 24.13 mm (27.3%). Low PB subjects thought large buttons were better
and made the touching operation easier. Some High PB subjects also mentioned the
comfort and ease of use of larger buttons, but were concerned that very large buttons
are less convenient because a large space that must be searched in order to use them.
Overall Button Spacing Prefernces. A Chi-Square Test revealed a significant
difference in preferred button spacings, x2 = 35 df = 4, P*** < .001. Fourty-
four percent of the subjects preferred a spacing of 6.35 mm, 17.5 percent preferred
3.17 mm and 21.25 percent preferred 12.7 mm. Note these are all in the middle of the
range of spacings tested.
Analysis also revealed no significant difference between the preferred horizontal
spacing and the preferred vertical spacing, x2 = 0.512 df = 4, P > .05.
Manual Dexterity and Button Spacing Preferences. Analyzing the preferences of each
PB group separately revealed a significant difference between High PB group and
Low PB group, x2 = 26.713, df = 4, P*** < .001. Compared to High PB group, the
Low PB group preferred larger button spacings. The High PB group preferred
spacings of 3.17 mm (30.56%) and 6.35 mm (58.33%). In the Low PB group,
spacings of 6.35 mm (31.82%), 12.7 mm (34.09%) and 19.05 mm (25.00%) were
significantly preferred over the other spaces.
4 Recommendations and Discussions
4.1 Button Size
It was hypothesized that older adults would have shorter reaction times with larger
touch-sensitive buttons was supported by the experiments, which is consistent with
940 Z.X. Jin, T. Plocher, and L. Kiff
previous studies [4,5,6,7,8,9]. Accuracy of performance presented a noisier and
slightly more complicated picture. The older adults in Experiment 2 did not perform
with significantly more accuracy as button size increased. However, they were most
accurate with buttons that were 19.05 mm square. In addition, consistent with
previous studies [4,5,6,7,8,10], the majority of the subjects expressed a preference for
buttons that were large, but not too large, 16.51 mm and 19.05 mm square.
What design guidelines for sizing touch-sensitive buttons can be stated based on
the results of these two experiments? First, if one is designing a separate button with
no adjacent buttons, and a reaction time of around 1400 ms is acceptable, then an
acceptable minimum button size is 11.43 mm square. A larger button size, such as
19.05 mm square, should be used if the task requires better performance. Second, if
the user interface design uses rows of adjacent buttons and screen space is limited,
then a button size of 16.51 mm square is acceptable. Again, if faster response
performance is required, then a larger button size, such as 19.05 mm square, should
be used. The experiment results show that buttons of this size also produce the highest
accuracy of response and are quite preferred by older users.
4.2 Spacing
It was hypothesized that larger spaces between touch-sensitive buttons must improve
the touch screen performance of older adults generally was not supported. The
subjects had longer reaction times with larger spaces between buttons. This is
consistent with Sun's [9] findings with younger subjects. Martin, et al. [6] have
explained similar findings in terms of Fitts' Law [17].
What guidelines for touch-sensitive button spacing can be derived from these
experiments? If the user interface design uses rows of adjacent buttons on a single
screen, then the buttons should be separated by a space of 3.17 mm to 12.7 mm. Older
adult subjects preferred a spacing of 6.35 mm for this kind of button layout and also
were most accurate with this spacing. Large spacing (19.05 mm in this experiment)
will only increase the time for searching the screen and moving to touch the target
button. Designers should be cautious of using no space between buttons. Although
zero spacing did not affect response speed in these experiments, it was associated
with the lowest accuracy and the lowest preference ratings.
4.3 Manual Dexterity
Manual dexterity will not significantly affect the performance of touching an isolated
button on the touch screen, but it has a significant effect on speed and a slight effect
on the accuracy of selecting and touching a target button embedded in a row of
adjacent buttons. Scores on the Peg Board tests were an effective way to categorize
older adults according to their manual dexterity. The High Peg Board Test subjects
were able to touch the target button more accurately and more quickly and preferred
relatively smaller buttons and spacings. Subjects in the Low Peg Board Test group
touched the buttons more slowly and preferred relatively larger buttons and spacings.
These results suggest that a designer who applies these button size and spacing
guidelines needs to be cognizant of the target population for his or her design. If the
target is older adults with relatively normal manual dexterity, then a button size of
Touch Screen User Interfaces for Older Adults: Button Size and Spacing 941
16.51 mm and spacing of 3.17 mm to 6.35 mm should be appropriate for screen
layouts that require rows of adjacent buttons. However, for older adults with poor
manual dexterity a larger button size, at least 19.05 mm and a larger spacing, 6.35 mm
to 12.7 mm, is required.
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... Other researchers believed that a button with a size of 19.05 mm and a gap of 6 mm is best [23]. Moreover, researchers found that, when the button size was 17.5 mm and larger (e.g., 19.05 mm and 20 mm), better user performance could be generated under different levels of button spacing [24][25][26]. Thus, there is no consensus on button size among these standards and previous studies. ...
... Yueh [28] found that, compared with young people, the elderly preferred larger buttons with a side length of 20 mm when using touchscreens. Jin [25] found that, for the elderly with normal finger movement, a button size of 16.51 mm was best, whereas, for the elderly with low finger flexibility, a button size of at least 19.05 mm was required. Other studies considered posture. ...
... All participants had difficulty in recognizing the smaller 10 mm button size. This was consistent with previous studies [23][24][25]27,28]. There was almost no difference in accuracy when using 15 mm, 20 mm, and 25 mm buttons among users, especially among young people. ...
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Touch technology-based smart homes have become increasingly prevalent, as they can help people with independent daily life, especially for the elderly. The aim of this study was to investigate the effects of button features (i.e., button size, graphics/text ratio, and icon style) in smart home interfaces on user performance across two age groups. Participants in the young group (n = 15) and senior group (n = 15) completed a clicking task. Button size ranged from 10 mm to 25 mm with 5 mm increments. The three levels of graphics/text ratio were 3:1, 1:1, and 1:3, while icon style was either flat or skeuomorphic. Results showed that button size and graphics/text ratio had significant effects on user performance in both groups, whereas icon style only had an effect in the senior group. It was observed that the elderly were fond of buttons with a larger size of 20 mm with larger texts and skeuomorphic icons, whereas the young preferred a button size of 15 mm with equal-sized graphics and text. These results may help to improve the accessibility and usability of smart home interface design.
... The touchscreen seems a part of life because it is employed in many different applications used in daily life, such as mobile phones, tablets, kiosk displays, ATMs, and home systems [1]. In recent years, the integration of touchscreen into flight decks has also started. ...
... They pointed to 17.5 mm as the optimal size for touchscreen use. Jin et al. [1] reported that 16.51 mm square is acceptable for a touchscreen interface. Chen et al. [14] studied button size ranging from 10 to 30 mm with 5-mm increments; the results demonstrated that 15 mm is acceptable for healthy individuals. ...
... In addition, the participant groups mentioned above do not consist of pilots, except for Dodd et al.'s [5] study. Jin et al. [1] suggested designers who implement button size and button spacing guidelines to be conscious of the design's target population. Considering these, it is difficult for human factors practitioners to identify optimal touchscreen target size for touchscreen, especially in the flight deck of fighter aircraft. ...
Chapter
The popularity of integrating touchscreen technology into next-generation fighter aircraft’s flight decks has increased recently. Therefore, the touch button size and button spacing have gained importance in human factors. In this way, the current study aimed to investigate the optimal button size and button spacing for next-generation fighter aircraft’s touchscreen. In accordance with that purpose, fourteen participants consisting of flight test engineers and pilots performed experimental tasks in a flight simulator on the six different keyboard designs consisting of three different sized buttons (12.7 mm, 15.87 mm & 19.05 mm) and two different sized spacing (1.65 mm & 2.54 mm). Dependent variables consisted of task completion time, total errors, subjective workload scale scores, and user preference. A button size of 12.7 mm and a button spacing of 2.54 mm are optimal when considered task completion time and workload. No significant difference was found in terms of total error. Participants mostly favored a button size of 15.87 mm. Optimal button size and button spacing can be affected by the factors such as maneuvering and pilot equipment (e.g., gloves). Hence, it is recommended that human factors researchers replicate this study by manipulating these factors, especially in simulator settings with jet fighter pilots.
... Key size is recommended to be larger than 9.5 mm in the American Standard ANSI/HFES 100-2007, and there is no significant improvement in interaction performance when the size is larger than 22 mm. Regarding the key spacing, it is basically concluded in existing studies that there is no significant difference between different key spacing for user interaction performance [33,34]. ...
... At the outset, the normality test is carried out for the proportion of points of view of quantitative data. Since the sample size is less than 50, the Shapiro-Wilk normality test is used to test whether the data at this stage have the nature of normal distribution [34]. The p-value of the number of points of view of quantitative data is less than 0.05, the absolute value of kurtosis is is less than 10 and the absolute value of skewness is less than 3, indicating that although the data are not an absolutely normal distribution, they can basically be accepted as the normal distribution. ...
Article
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The concept of the smart home has been widely recognized and accepted, but the differentiated characteristics of elderly smart products in terms of demand and use are becoming more and more prominent. The lack of an efficient navigation design of the smart product interface increases the cognitive burden of elderly users, and how to better meet the needs of the elderly with smart products gradually becomes the focus of attention. This study was conducted for the elderly group, using the scenario-based design method to analyze the needs of elderly users, combining the research results of scenario theory with the smart home interaction design research method, focusing on how to make the style of interface navigation, sliding layout and button size more suitable for the cognitive behavior of elderly users. The purpose of this research is to realize an age-friendly smart home interaction design in terms of functional design and interface design. The experiment is divided into two stages: in stage 1, two different layouts and operation methods are commonly used for the age-friendly smart home interface: up and down sliding and left and right sliding; in stage 2, the functional buttons are square, where 4 styles are selected, and the side lengths are set to 10 mm, 12 mm, 15 mm, 18 mm and 22 mm. The sliding and retrieval test and retrieval and click test results show that for different sliding layout methods, the interactive performance and subjective evaluation of the interface with the up-and-down sliding layout are better. Among all functional button styles, the interaction performance and subjective evaluation of the simple button style with lines are the best. Among the function keys with a size of 10–22 mm, the interaction performance is better from 12 mm to 18 mm. The conclusion of the better interface data information obtained from this experiment improves the rationality of the age-friendly smart home interface and makes the smart home interface better for the age-friendly scenario.
... Precise click calibration. As applications become more complicated these days, there are often multiple UI components crammed into one interface making it crowded including small icons which are hard to click on precisely especially for older adults [26]. Therefore to improve the correct rate of clicks, we design an algorithm to discriminate which icon is the one that the user is meant to click on as Fig. 4 b shows. ...
Article
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As smartphones are widely adopted, mobile applications (apps) are emerging to provide critical services such as food delivery and telemedicine. While bring convenience to everyday life, this trend may create barriers for older adults who tend to be less tech-savvy than young people. In-person or screen sharing support is helpful but limited by the help-givers' availability. Video tutorials can be useful but require users to switch contexts between watching the tutorial and performing the corresponding actions in the app, which is cumbersome to do on a mobile phone. Although interactive tutorials have been shown to be promising, none was designed for older adults. Furthermore, the trial-and-error approach has been shown to be beneficial for older adults, but they often lack support to use the approach. Inspired by both interactive tutorials and trial-and-error approach, we designed an app-independent mobile service, Synapse, for help-givers to create a multimodal interactive tutorial on a smartphone and for help-receivers (e.g., older adults) to receive interactive guidance with trial-and-error support when they work on the same task. We conducted a user study with 18 older adults who were 60 and over. Our quantitative and qualitative results show that Synapse provided better support than the traditional video approach and enabled participants to feel more confident and motivated. Lastly, we present further design considerations to better support older adults with trial-and-error on smartphones.
... or 12mm (ID=5.0) wide, based on relevant literature (Jin, Plocher & Kiff, 2007;Sesto, Irwin, Chen, Chourasia & Wiegmann, 2012), and presented as structured or unstructured arrays of 1, 4, 9 or 25 similar targets, arranged in a uniform square. Indices of difficulty (IDs) were calculated based on the width of the target and the distance from the participant's hand to the target when their hand was placed on the steering wheel at the "10 o'clock" position, in line with Fitts (1954). ...
Conference Paper
Theoretical techniques to model and predict drivers' visual behaviour during the execution of secondary in-vehicle tasks, such as the extended keystroke level model (eKLM), are predicated on perfect task resumability during the interleaving of attention, i.e., it is assumed that the secondary task can resume without penalty-irrespective of task characteristics-as soon as attention is redirected to it. In practice, this is unlikely to be the case. Moreover, it is reasonable to opine that resumability may improve over increasing numbers of glances. A formative occlusion study was devised to explore search-and-touch HMI interactions in which the number of glances and task complexity varied, with the aim of deriving new eKLM resumability operators.
... Furthermore, using our prototyping tool, Figma 1 , we checked if our selected color scheme would be distinguishable for individuals with color blindness. Buttons were designed to be larger than 19.05 mm in both length and width, with the goal of being easily selectable for older adults and individuals with MCI (Jin et al., 2007). Finally, we tried to adopt a minimalist design for reminder interfaces to avoid overwhelming our users with unnecessary visual elements. ...
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Many individuals with mild cognitive impairment (MCI) struggle with the decision to cease driving prematurely due to cognitive deficiencies in processing speed, memory, attention, judgment, or visuospatial skills. Highly automated vehicles (AVs) can be used as assistive technologies for individuals with MCI, performing all driving tasks for them, and extending their safe and independent mobility. However, use of highly AVs introduces a different set of challenges than manual driving. These challenges rely more heavily on memory and decision-making abilities of its users. Therefore, the objective of this study was to investigate the barriers that individuals with MCI face when interacting with highly AVs to support the design of in-vehicle interfaces that will help users with non-driving related travel tasks. Specifically, we aimed to design a system for providing reminders and other guidance to individuals with MCI during solo trips in personally owned or private AVs. To achieve this goal, we conducted individual interviews with experts in driving rehabilitation, rehabilitation professionals, and academics with a focus on assistive technologies, rehabilitation sciences, engineering, and inclusive design ( N = 7). The thematic analysis of the data from these subject matter experts highlighted the necessity for reminders, defined as system-initiated prompts that assist individuals with remembering or acknowledging a specific piece of information, and resulted in a set of user needs. We then created a set of prototype interfaces based on these user needs that help individuals with MCI complete their trips by providing reminders of important trip related information. The reminders system was designed to be displayed on a central dashboard display placed in front of the passenger’s seat and present important information that address the users’ difficulties with prospective memory, remembering and understanding the features of the highly AV, and understanding the current trip status. This study serves as an initial investigation into ensuring that the experience of using highly AVs is inclusive and can support the needs of individuals with MCI. The designed interactions proposed by the reminders system can serve as a platform for future in-vehicle interfaces.
... Touch screen interfaces are increasingly utilised to assist in the usability of technology for older adults as they require direct input, have large button targets and eradicate the need for a monitor, mouse and keyboard (Jin et al. 2007 However, Newell (2008) argues that differences exist between mainstream technology and assistive technology thus those that infer universal usability are not being realistic. ...
Thesis
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The potential of developing new technologies that may assist people living with dementia to successfully navigate their day is increasingly recognised. Interventions include prompts and reminders to support memory function as well as safety detectors and activity monitors. Few however, have recognised the potential of using existing technologies as an intervention to support social interactions and enjoyable activities. This thesis explored the potential of touch screen computer technology in facilitating enjoyable activities with people with dementia who live in the community. The project premise that technology may facilitate enjoyable activity by those with a dementia diagnosis was explored through two successive studies. The first involved attendees at a community day care centre. They were living with moderate to later manifestations of the condition but still lived at home, some alone. The second study involved people with a recent diagnosis of dementia and participants took part in their own homes. The methodology employed was a focused visual ethnography and data collection methods comprised of video-based participant observations and in-depth interviews. Data analysis required the development of a novel technique drawing on concepts of multimodality and visual ethnographic methods which enabled non-verbal behaviour to be represented as equally significant to verbal behaviour. Findings from study 1 indicate that activities were enjoyed ‘in the moment’. Although familiarity of the devices and applications was observed within sessions this did not extend between sessions. Further, the group context in study 1 provides regular social contact for people experiencing life in similar ways. In contrast, findings from study 2 indicated that the use of new knowledge and retained learning occurred across sessions for all participants, irrespective of the style of technology engagement. Nevertheless, the majority of participants in study 2 reported feeling lonely as a consequence of the condition and in need of increased social contact. The conclusions reached suggest that touch screen technology can facilitate enjoyable activities with people living with dementia, irrespective of the level of impairment, if supported appropriately.
Chapter
This article investigates tactile interaction on smartphones with adults aged 65 or older who were considered to have a novice level of skill with technology. Two experiments with two different groups of 40 Portuguese adults adds empirical evidence to the field and shows that older adult performance for tapping is best toward the center, right edge, and bottom right corner of the smartphone display. Results also show that a participant's performance of horizontal swipes is better with targets toward the bottom half of the display, while participant's performance of vertical swipes is better with targets toward the right half of the display. This article contributes to the body of research on the design of user interfaces for smartphones and mobile applications targeted at older adults, as well as providing practical information for designers and practitioners developing products that are more universally accessible.
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Smart homes represent an effective approach to improve one’s quality of life. Developing user interfaces that are both comfortable and understandable can assist users, particularly the elderly, embrace smart home technologies. It’s critical to concentrate on the characteristics of smart home interface design and their impact on people of various ages. Since sliders are one of the most common components utilized in the smart home user interface, this article aimed to investigate the effects of slider design characteristics (e.g., button size, track color, and sliding orientation) on user performance and preference. Thirty-four participants were recruited for the experiment (16 for the young group, aged between 18 and 44 years; 18 for the middle-aged and elderly group, aged between 45 years and above). Our results revealed that both groups had shorter task completion time, less fixation time, and saccades on horizontal sliding orientation and larger buttons, which means better user performance. For the older group, the slider with color gradient track led to better user performance, while the track color only had less effect on the performance of the younger group. In terms of user preference, the results and performance of the older group were basically consistent, while the younger group had no significant difference in sliding orientation and track color.
Article
Background and objective As cognitive, motor, and sensory skills decline with age, the interface needs of elderly users differ from that of young adults, especially when entering important information in healthcare applications (e.g. blood glucose values) via a numeric keypad on a smartphone touchscreen. The aim of this study is to propose an optimal numeric keypad design for elderly users. A total of 51 participants greater than or equal to 65 years old completed a 6-digit numeric entry task on a smartphone touchscreen. The Java-based experimental program allows participants to operate 45 different keypad designs consisting of three button shapes (circle, vertical rectangle, and square), five button sizes with 2.5-mm increments (7.5 mm, 10 mm, 12.5 mm, 15 mm, and 17.5 mm), and three button spacings (0 mm, 1 mm, and 3 mm). The usability of the keypad design was compared based on task completion time, error rate, and subjective satisfaction, while the data was analyzed using repeated measures ANOVA. The results show that circle and square buttons outperform the vertical rectangle button in completion time, accuracy, and satisfaction. Square and circle buttons in 15 mm size led to improved efficiency and decreased error rate. Moreover, task completion time for 3 mm is significantly shorter than 0 mm spacing. Given sufficient space on the touchscreen, the 3 mm spacing can be considered optimal when designing a numeric keypad interface. This study presents a comparison of different numeric keypad designs and the impact on the performance and satisfaction of elderly users. The result can be applied to smartphone numeric keypad design to increase input accuracy and speed. In addition, both circle and square buttons can be adopted in user interfaces for elderly users without the decline of usability. Relevance to industry The proposed configuration of button shape, size, and spacing can be applied to the numeric keypad user interface (UI) of smartphones targeting elderly users, especially in healthcare applications.
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Touch screen input keys compete with other information for limited screen space. The present study estimated the smallest key size that would not degrade performance or user satisfaction. Twenty participants used finger touches to enter one, four or 10 digits in a numeric keypad displayed on a capacitive touch screen, while standing in front of a touch screen kiosk. Key size (10, 15, 20, 25 mm square) and edge-to-edge key spacing (1, 3 mm) were factorially combined. Performance was evaluated with response time and errors, and user preferences were obtained. Spacing had no measurable effects. Entry times were longer and errors were higher for smaller key sizes, but no significant differences were found between key sizes of 20 and 25 mm. Participants also preferred 20 mm keys to smaller keys, and they were indifferent between 20 and 25 mm keys. Therefore, a key size of 20 mm was found to be sufficiently large for land-on key entry.
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Designing numeric keypads for point-of-sale devices to optimize keying speed and accuracy while efficiently utilizing touch screen real estate is a challenge. Existing design guidelines for touch screens are applicable to only specific classes of devices and fail to consider user variables such as finger size. The present study investigated keying speed and error rates for various keypad configurations in a simulated retail keying task. Finger sizes were taken into account. Results support the use of compressed (2 mm or less) interkey spacing in keypad designs. No significant effects of key size were found. Gender differences in keying speed and accuracy were explained by finger size differences between males and females. Implications for the design of touch screen user interfaces in point-of-sale applications are discussed.
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Within recent years, the advent of microprocessor technology and reduction in cost of optical electronic devices has allowed Touch Screen Devices (TSD's) to become a viable option for person-computer interface. Basically, TSD's consist of any of a number of different technologies that can overlay a CRT which permits an operator to make a selection by touching a predesignated area of the CRT screen. To date, the authors have performed a literature search, user interviews and field evaluations of TSD's and have noted a variety of advantages/disadvantages associated with the technologies available and problems with the selection/implementation of TSD's.
Accuracy of input using touch panel devices is affected by a number of variables which include device type, target size, and target location. It was also hypothesized that instructional set should influence performance. A screening experiment using a central-composite design (CCD) was conducted to further examine the effects of target position and size upon accuracy of the touch input. Results suggest that error for right-handed users is least near the resting position of the hand (lower right corner of display) and that shortest response times could also be obtained there. Variations in size were more likely to affect error in the y axis and quadratic effects were present. It was also found that although instructions requiring higher precision of input from the operator did not substantially affect bias error, they did produce a reduction in variable error. It is recommended that for applications having established key input areas, positions along the lower and right-hand borders of the control/display unit should be used to minimize activation time and error. Use of the lower border exclusively can accomodate users with either a right-hand or left-hand preference. Some comments are also provided on the limitations which bound the interpretation of results in several studies and inferences thus drawn.
Although human performance on keyboards, pointing devices, and touch screens in the desktop environment has been studied and reported to the extent that the results can be used to determine productivity rates from those devices, little research has been conducted on devices used in controlled environments, like that of point-of-sale in the retail industry. While previous devices available for user interaction in this environment have been 2×20 displays and industry specific keyboards, current technology has moved the industry to implement CRTs, LCDs, full keyboards, touch screens and uniquely designed devices like the NCR DynaKey, an integrated LCD, keypad and dynamically assignable function keys. A full understanding of human performance on these devices was required to aid retailers in cost justifying their investment in them. Laboratory research was conducted to compare performance of basic point-of-sale tasks on a CRT with 56-key keyboard, 3 versions of an LCD touch screen, and the NCR DynaKey. Participants performed keying tasks, item modification tasks, a combination of item modification and scanning, and the same combination of item modification and scanning with a secondary monitoring task imposed. Time and error rates showed significant differences among the user interface devices for each of the task requirements in this research. Overall, mechanically keyed numeric entry was superior to touch screen numeric entry, mechanical keys were more advantageous with increased skill levels, and the integration of input mechanism and display as well as direct mapping between input and display enhanced performance.
Conference Paper
Two experiments were performed to assess the effects of touch key design parameters on menu-selection error rates, The first experiment determined that the optimal design consisted of touch keys 10,16-mm high, either 10,16- or 20, 2- wide, and separated vertically by less than 10,16 mm, The second experiment extended the investigation by including the effects of viewing angle, These latter results replicated the first experiment, but also favored the 2012-mm wide key for off-axis viewing conditions, In both experiments, the horizontal separation between touch keys did not affect menu-selection accuracy; however, subjective selection favored a 20.32-mm horizontal separation.
Conference Paper
For the convenience of firefighters’ decision-making and operation, touch screen display was chosen as the preferred interface for a fire information display system. Few studies were conducted to determine comfortable button/icon size on touch screens. This experiment investigated the effect of four factors on operators’ performance with touch screen: 1) button size (20*20, 30*30, 40*40, and 50*50 pixels 2), spacing between buttons (0, 5, 10, and 20 pixels), 3) button/icon types (digit buttons only, picture icons only, combination), and 4) glove wearing (wearing vs. not wearing). 14 males were asked to accomplish a series of matching tasks on touch screen with the forefinger of right hand. Results showed that the spacing between buttons/icons, and wearing or not wearing a glove did not affect performance. Subjects pointed to the digit buttons faster than the other two kinds of buttons/icons. There was a significant difference among button/icon sizes. People performed best when it was equal to or bigger than 40*40 pixels.
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This paper reports on a study comparing keying accuracy and speed for eight different numeric keypad configurations on a touch screen. Using touch-sensitive keypads displayed on a computer terminal, operators entered numbers presented to them through a speech synthesizer. Dependent measures collected were keying rates, errors, and the x- and y-dimension standard deviations from the centre point of the key. The primary finding was that keypads with square keys resulted in improved speed and a higher degree of accuracy than do keypads with regular keys (either a long horizontal dimension or a longer vertical dimension). Spread-out versions of the keypads (inter-key spacing = 1·3 cm) did not yield superior performance compared with compressed versions (inter-key spacing = 0·6 cm). © 1988 S.Vldaček, L.Kaliterna, B.Radosšvić-Vidaček, S.Folkard.
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Thesis (Ph. D.)--Wichita State University, College of Liberal Arts and Sciences. Spine title: Touch screen performance. "Spring 1999." Includes bibliographical references (leaves 69-76).
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Reports of 3 experiments testing the hypothesis that the average duration of responses is directly proportional to the minimum average amount of information per response. The results show that the rate of performance is approximately constant over a wide range of movement amplitude and tolerance limits. This supports the thesis that "the performance capacity of the human motor system plus its associated visual and proprioceptive feedback mechanisms, when measured in information units, is relatively constant over a considerable range of task conditions." 25 references. (PsycINFO Database Record (c) 2006 APA, all rights reserved).